You should be ok guys.
I installed service pack 3, 2 weeks ago after resisting as long as I could.
Everything is working normally on my computer and it should be much more secure.
My only problem (which is my own doing) is that I've set my security level on Internet Explorer to HIGH and it won't let me look at some things on some sites (such as You-Tube).
I then have to lower security to do certain things and then raise it again immediately afterwards. Better safe than sorry!
Tony, Sheffield UK